Capacity control operating mechanism for centrifugal compressor

ABSTRACT

The capacity control means of a centrifugal gas compressor is connected to a reversible motor by motion transmitting means including a crank structure which functions to move the control member slowly as it approaches and leaves closed position. During that portion of the movement of the control member, the torque applied thereto by the motor is multiplied, permitting the use of a small motor.

United States Patent Inventor Edson H. Byrns Fayettevllle, N.Y.

Appl, No. 60,482

Filed Aug. 3, 1970 Patented Dec. 7, 1971 Assignee Carrier CorporationSyracuse, N.Y.

CAPACITY CONTROL OPERATING MECHANISM FOR CENTRIFUGAL COMPRESSOR 4Clnlms, 2 Drawlng Figs.

int. Cl F04d 27/00 Field of Search 415/ 147,

References Cited UNITED STATES PATENTS 2/1958 Christensen 6/1960 Howell10/1961 C0lley....

1/1968 Endress.. 4/ l 968 Geyer FOREIGN PATENTS 6/1943 Germany PrimaryExaminerHenry F. Raduazo Attorneys-Harry G. Martin, Jr. and J. RaymondCurtin ABSTRACT: The capacity control means of a centrifugal gascompressor is connected to a reversible motor by motion transmittingmeans including a crank structure which functions to move the controlmember slowly as it approaches and leaves closed position. During thatportion of the movement of the control member, the torque appliedthereto by the motor is multiplied, permitting the use ofa small motor.

PATENTEDUEE mu 3.625628 SHEET 1 [IF 2 IN VENTOR. EDSON H. BYRNS ATTORNEYPATENTEDUEU 'HHTI SHEET 2 OF 2 IIIIIIIIIILIIIIII Il/Ilfllllll FIG. 2

INVENTOR. EDSON H. BYRNS ATTORNEY CAPACITY CONTROL OPERATING MECHANISMFOR CENTRIFUGAL COMPRESSOR BACKGROUND OF THE INVENTION Many actuatingmechanisms have been devised and used for operating capacity controlmeans of centrifugal compressors. Such control means includes guidevanes and dampers arranged in the inlet of the compressor and diffuservalve structures arranged in the discharge diffuser of the compressor.In regard to the diffuser valve control mechanism, the movement thereofbetween open and closed positions may be at a uniform rate; and thetorque required for such movement is substantially uniform.

However, in regard to inlet capacity control vanes and butterfly valvesor dampers mounted in the compressor inlet, such devices are verysensitive to the gas flow when they are moved in the area near closedposition; and it is, therefore, desirable to move the control membervery slowly in this area, particularly in moving it from closedposition. Also, movement of the control member in proximity to theclosed position requires the application of substantially more torquethan in actuating the member throughout the remainder of its movement.

This invention has as an object a capacity control actuating mechanismembodying an arrangement where the member is operated by a relativelysmall reversible motor connected to the member by motion transmittingmechanism which functions to effect slow movement of the control memberby the constant speed motor when the member is traveling in proximity tothe closed position; and, during movement in that area, the torqueoutput of the motor is multiplied, permitting the economical use of asmall motor.

SUMMARY OF THE INVENTION The capacity control operating motor and thecontrol member are provided with radially extending arms connectedtogether to impart oscillation to the shaft to which the control memberis fixed. The motor output shaft is so located relative to the operatingshaft of the control member, and the motion transmitting arms connectedto the motor and the control member are so arranged that as the controlmember approaches and leaves closed position, the movement of the memberis reduced in speed and a greater torque leverage applied to theoperating shaft of the control member.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a vertical sectional view ofthe intake end of a centrifugal gas compressor of conventional form, theview including the control means operating mechanism embodying ourinvention; and

FIG. 2 is a view of the operating mechanism taken on line 2-2 of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. I, designatesthe intake section of the centrifugal compressor, the section 10 beingattached to a section 11 as by means of cap screws 12. The section 11encircles the impeller 13 fixed to the shaft 14 journaled in the mainframe 15 of the compressor and to which the section 11 is attached as bycap screws 17.

The capacity control means is illustrated as a butterfly valve or damper23 formed with a trunnion 25 journaled in one side of an annular member26 mounted intermediate the section 10 and a section 27 as by screws 28.An actuating shaft 29 extends from the opposite side of the valve and isjournaled in like manner in the frame member 26, and has an outwardlyextending portion 30 to which is affixed a driven arm 31 as by means ofthe key 33. The arm 31 extends outwardly from the shaft 30' (see FIG. 2)and has a sliding connection with a block 35 formed with a trunnion 36journaled in a drive arm 37.

The control operating mechanism is mounted in a sheet metal enclosure38, the bottom wall 39 of which is attached to the section 26 as byscrews 40. The frame work also includes a bracket member 43 to which agear casing 45 is attached as by screws 47. A motor is attached to thegear box 45 to power the output shaft 51.

The drive arm 37 is fixed to the shaft 51 as by a set screw 53, the arm37 being apertured to rotatably receive the trunnion 36 of the block 35.

The motor output or power shaft 51, and the valve shaft 30 are solocated relatively, and the arms 31, 37 are so fixed to the shafts, thatupon movement of the drive arm 37 in a clockwise direction (FIG. 2) forthe transmission of similar movement to the driven arm 31 and shaft 30,the speed of such movement of arm 31, and accordingly, damper 23 isreduced as the mechanism approaches the closed damper position as willbe apparent from a consideration of FIG. 2 of the drawings. The motoroutput shaft 51 is journaled in parallel spaced relation to the shaft 30(see FIG. 1). When the capacity control member 23 is moved to the closedposition, the arms 31, 37 are moved to the position shown in dottedoutline at the left in FIG. 2, this position being indicated by thelegend "closed position. When the control member has been moved to theopen position, the arms 31, 37 are positioned as shown in dotted outlineat the right of FIG. 2, designated by the legend open position.

As the control member 23 is moved between open and closed positions, thedriven arm 31 is moved through an arc indicated by the dotted line 54.The motor output shaft 51 is positioned a distance from the planeindicated by the line 55 extending through the axis of shaft 30 andbisecting the are 54. As illustrated in FIG. 2, the shaft 51 is spacedfrom the plane 55 in a direction toward the open position, and locatedin the sector in which the arm 31 moves.

With this arrangement, as the driver arm 37 is moved in a clockwisedirection (FIG. 2), the block 35 is moved along the arm 31 toward theshaft 30. During this movement, the arm 31 is also moved in a clockwisedirection, eflecting movement of the valve 23 toward closed position.Upon reversal of motor 50, the arms 31, 37 are moved in acounterclockwise direction. Movement of these parts is limited in bothdirections by the outer end of the arm 37 engaging the actuating membersof limit switches 60, 61. The switch is positioned to be engaged by thearm 37 when the valve 23 is moved to closed position. The switch 61 isactuated when the valve is moved to open position.

As previously stated, the arm 31 is movable through an are indicated at54. Due to the location of the motor drive shaft 51 and the valve drivenshaft 30 as described, the valve shaft 30 is rotated slower as the valve23 moves in the area of the closed position. The motor 50 is operated ata constant speed in both directions. Therefore, the valve 23 is movedslowly in the vicinity of the closed position. This is particularlyadvantageous when the compressor control means is in the form of abutterfly valve or damper, as the valve is very sensitive to flow whenit is moved in the vicinity of the closed position. With the arrangementdescribed, the first l0 of the valve movement, from closed positiontoward open position, the shaft 51 rotates 43 the ratio being betterthan 4 to I.

Also, the greatest torque required to rotate the valve is when it is at,or near, the closed position. The compressor capacity control operatingmechanism embodying my invention permits the motor to deliver greatertorque to the valve as it is moved toward closed position. It will beapparent that my capacity control operating mechanism is equally usefulin operating conventional inlet guide vanes and annular diffuser valves.The capacity control operating mechanism of my invention obviates theneed of expensive percentage timers or the like. It will be understoodthe motor 50 is controlled by means sensing the demand load on thecompressor.

1 claim:

1. Mechanism for operating capacity control means for a centrifugalcompressor, said control means being movable between open and closedpositions, comprising a frame, an actuating shaft journaled in saidframe and being operatively connected to said control means, a powershaft journaled in said frame in spaced relation to said actuatingshaft, motion transmitting linkage connecting said power shaft to saidactuating shaft, a reversible constant speed motor connected to saidpower shaft and operable when energized to effect oscillation of saidpower shaft, said motion transmitting linkage including means operableto reduce the speed of motion of said control means during movementthereof in the vicinity of the closed position.

2. Mechanism for operating capacity control means for a centrifugalcompressor, said control means being movable between open and closedpositions, comprising a frame, an actuating shaft joumaled in said frameand being operatively connected to said control means, a power shaftjournaled in said frame in spaced parallel relation to said actuatingshaft, a drive arm fixed to said power shaft and extending therefrom formovement in a plane normal to the axis of said shaft upon oscillationthereof, a driven arm fixed to said actuating shaft and extendingtherefrom for oscillating movement in a plane normal to the axis of saidactuating shaft, said driven arm being operatively connected to saiddrive arm and being movable upon oscillation thereof through an arebetween open and closed stop positions corresponding to the open andclosed positions of said control means, the axis of said power shaftbeing located within the sector of movement of said driven arm andspaced in the direction toward said open stop position a distance fromthe plane extending through the axis of said actuating shaft andbisecting said are, and a reversible motor connected to said power shaftand operable to effect oscillation thereof.

3. Mechanism for operating capacity control means for a centrifugalcompressor as set forth in claim 1 wherein said driven arm is mountedfor oscillation in a plane spaced outwardly from said drive am in adirection axially of said power shaft.

4. Mechanism for operating capacity control means for a centrifugalcompressor as set forth in claim 1 wherein the connection between saiddrive arm and said driven arm includes a block pivotally mounted on saiddrive arm and being formed with a through aperture, said driven armextending through said aperture and having sliding connection with saidblock.

1. Mechanism for operating capacity control means for a centrifugalcompressor, said control means being movable between open and closedpositions, comprising a frame, an actuating shaft journaled in saidframe and being operatively connected to said control means, a powershaft journaled in said frame in spaced relation to said actuatingshaft, motion transmitting linkage connecting said power shaft to saidactuating shaft, a reversible constant speed motor connected to saidpower shaft and operable when energized to effect oscillation of saidpower shaft, said motion transmitting linkage including means operableto reduce the speed of motion of said control means during movementthereof in the vicinity of the closed position.
 2. Mechanism foroperating capacity control means for a centrifugal compressor, saidcontrol means being movable between open and closed positions,comprising a frame, an actuating shaft journaled in said frame and beingoperatively connected to said control means, a power shaft journaled insaid frame in spaced parallel relation to said actuating shaft, a drivearm fixed to said power shaft and extending therefrom for movement in aplane normal to the axis of said shaft upon oscillation thereof, adriven arm fixed to said actuating shaft and extending therefrom foroscillating movement in a plane normal to the axis of said actuatingshaft, said driven arm being operatively connected to said drive arm andbeing movable upon oscillation thereof through an arc between open andclosed stop positions corresponding to the open and closed positions ofsaid control means, the axis of said power shaft being located withinthe sector of movement of said driven arm and spaced in the directiontoward said open stop position a distance from the plane extendingthrough the axis of said actuating shaft and bisecting said arc, and areversible motor connected to said power shaft and operable to effectoscillation thereof.
 3. Mechanism for operating capacity control meansfor a centrifugal compressor as set forth in claim 1 wherein said drivenarm is mounted for oscillation in a plane spaced outwardly from saiddrive arm in a direction axially of said power shaft.
 4. Mechanism foroperating capacity control means for a centrifugal compressor as setforth in claim 1 wherein the connection between said drive arm and saiddriven arm includes a block pivotally mounted on said drive arm andbeing formed with a through aperture, said driven arm extending throughsaid aperture and having sliding connection with said block.